A battery generates electrical energy by chemical action of electrodes of opposite polarity in an electrolyte. Sometimes a battery is short circuited, causing the battery to overheat. Overheating can result in the emission of an electrolyte, vapor, or molten electrode material. In some situations, explosions may occur. Thus, battery overheating can be dangerous to the user and others in the environment in which the battery is used.
U.S. Pat. No. 4,075,400 discloses a battery, comprising a lithium anode, a SOCl.sub.2 cathode and a woven electrically insulating separator. Overheating is prevented in this battery by the use of a thermal fuse. The fuse consists of a plurality of encapsulated particles containing a poisoning agent. The encapsulated particles are embedded in the fibers of the separator as particulate materials. When the battery of this patent reaches a predetermined temperature, the encapsulating materials release the poisoning agent. The released poisoning agent then deactivates the battery by shutting down current flow or combining chemically with one or more elements of the battery. The poisoning agent may be a wax.
However, tests have shown that the presence of unencapsulated particulate waxes on the separator or adjacent to a battery electrode can degrade the electrical performance of batteries. The average service life, energy delivered and peak power will be below that of batteries which include no particulated wax particles on the separator.
It is desirable to improve the performance of batteries having a thermal fuse.